Omission of fermentable carbohydrates from culture media of mammalian cell cultures elicts stimulation of a number of metabolic systems. The rate of uptake of labeled gallactose is increased. In glucose deprived hamster cells the labeled galactose tends to be oxidized via UDPGIucose to UDPGIucuronic acid (a donor of uronic acid units for hyaluronic acid). In normal glucose containing media addition of labeled galactose does not accumulate as UDPGIucuronic acid, but mainly as UDPGalactose, glycoproteins and a carrier lipid sugar molecule such as galactolipids. The latter may be related to retinyl phosphogalactose. Its identification is under investigation. The nature of the stimulation of transport and uptake in sugar deprived hamster cells might be revealed by studies on membrane vesicles from such cells. Bibliographic references: Silhavy, T.J., Boos, W., and Kalckar, H. M: The role of the Escherichia coli galactose-binding protein in galactose transport and chemotoxis. Biochem. of Sensory Functions "25 Mosbacher Colloquium", L. Jaenicke, Ed., Springer-Verlag, pp. 165-205, 1975. Ullrey, D., Gammon, M.T. and Kalckar, H.M.: Uptake patterns and transport enhancement in cultures of hamster cells deprived of carbohydrates. Arch. Biochem. Biophys. 167:410-416, 1975.